LOL see I prefer to try to change how people view the 12 instead of giving them "more" so they have the 16 or higher they want in half their scores.
I know it is all a matter of perspective of course.
I see a +1 as "the next level" above 0, and so on. In relative terms of Athletics, for instance:
-1 equals you sucked in gym class in high school.

+0 equals some high school sports in gym class.
+1 equals playing on a high school sports team.
+2 equals making the college sport team.
+3 equals making an amateur-pro team. (think minor league for baseball)
+4 equals making the pro team (the major league)
+5 equals making the all-starts roster.
Now, apply that "style of thinking" to ability scores instead. For most of the game, I think a +3 in your major ability score is very good and keeps the game a bit of challenge but not too hard. By the time you reach tier 3, you probably want to consider bumping it to +4, and +4 or even +5 is certainly recommended by tier 4 IMO.